|Publication number||US7436236 B2|
|Application number||US 11/144,373|
|Publication date||Oct 14, 2008|
|Filing date||Jun 3, 2005|
|Priority date||Jun 4, 2004|
|Also published as||CN1707963A, CN100380826C, DE602004025907D1, EP1603228A1, EP1603228B1, US20050271163|
|Publication number||11144373, 144373, US 7436236 B2, US 7436236B2, US-B2-7436236, US7436236 B2, US7436236B2|
|Original Assignee||Infineon Technologies Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (18), Referenced by (2), Classifications (6), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims priority to European Patent Application Serial. No. 04013261.5, filed Jun. 4, 2004.
The present invention relates an arrangement for an analog compensation of a DC component in an AC signal. The inventive arrangement comprises an estimating unit, a compensating unit and an adding unit, the estimating unit being adapted to produce an estimate corresponding to the DC component, the compensating unit being adapted to produce a compensating signal according to the estimate, and the adding unit being adapted to add the compensating signal to the AC signal.
There are applications where a DC offset inhibits performance thereby being unacceptable from a performance perspective.
The foremost applications for the present invention are Homodyne RF and high-end audio, but other areas might benefit as well. The most benefit is when there is a need to compensate for slow drifts like temperature.
Presently known solutions can generally be divided into two different approaches. One approach is continuously used where a high pass filter is blocking the DC component and letting the AC component pass. This approach will present problems with applications where there are low frequency components in the required signal, which thus will suffer if a high pass filter is coupled in the signal path.
Another approach is used only in the beginning of a process, such as in the set-up of a communication session, where an initial estimation of the DC component will be followed by a fixed compensation value used throughout the process. This latter approach suffers from long-term DC drifts or variations, such as temperature dependent variations, where the fixed compensation value will be unable to compensate for the changed DC component.
From the standpoint of the field of invention, as described above, the present invention teaches that the use of a version of the latter approach of solving the problem with an analog circuit that detects a DC drift and reiterates the estimation and compensation. The present invention uses a switch to update the DC compensation that does not disturb the signal unless it switches. The present invention is also made to avoid having the signal path go through it, which should ease the implementation requirements since it is easier to do a LF circuit.
An inventive arrangement for an analog compensation of a DC component in an AC signal comprises an estimating unit, a compensating unit and an adding unit. The estimating unit is adapted to produce an estimate corresponding to the DC component, the compensating unit is adapted to produce a compensating signal according to the estimate, and the adding unit is adapted to add the compensating signal to the AC signal. The present invention specifically teaches that the arrangement comprises a comparing unit, which is adapted to continuously compare the present estimate with the compensating signal.
If the difference between the present estimate and the compensating signal lies outside of a predefined interval, then the comparing unit is adapted to trigger the compensating unit to produce an updated compensating signal according to the present estimate, to switch from the present compensating signal to the updated compensating signal, and the adding unit is adapted to add the updated compensating signal to the AC signal.
If the difference between the present estimate and the compensating signal lies within the predefined interval, then the compensating unit is adapted to continue with the present compensating signal, and the adding unit is adapted to add the present compensating signal to the AC signal.
An advantage of the present invention is providing a possibility to continuously compensate for a DC component in an AC signal without putting an high pass filter in the signal path and with compensation for long term variations in the DC component.
An arrangement according to the present invention will now be described in more detail with reference to accompanying drawings, in which:
The arrangement comprises an estimating unit 2, a compensating unit 3 and an adding unit 4.
The estimating unit 2 is adapted to produce an estimate C corresponding to the DC component A, the compensating unit 3 is adapted to produce a compensating signal D according to the estimate C, and the adding unit 4 is adapted to add the compensating signal D to the AC signal B.
The present invention specifically teaches that the arrangement 1 comprises a comparing unit 5, which is adapted to continuously compare the present estimate C with the compensating signal D.
If the difference between the present estimate C and the compensating signal D lies outside of a predefined interval E, schematically shown in
If the difference between the present estimate C and the compensating signal D lies within the predefined interval E, then the compensating unit is adapted to continue with the present compensating signal D, and the adding unit is adapted to add the present compensating signal D to the AC signal B.
The interval E is adapted to allow a certain drift and ripple in the estimate C without triggering an update of the compensating signal D. The present invention does not specify the interval E since this is an application dependent parameter that will vary greatly between different applications of the present invention. It is however obvious for the skilled man how to set this parameter for a specific application of the invention.
The adding unit 4 comprises a smoothing unit 41 in order to provide a smooth transition between a recent compensating signal D and an updated compensating signal D′.
The invention could be implemented discretely with the circuit shown in
The invention also teaches that the comparator 5 is adapted to control a second switch S2, which second switch S2 is adapted to connect the estimating unit 2 to the AC signal B during estimation of the DC component A and disconnecting the estimating unit 2 from the AC signal B during update of the compensating signal D.
The first switch S1 will thus prevent noise from propagating to the adding unit 4 during estimation and the second switch S2 will prevent noise from interfering with the updating of the compensating signal D.
The adding unit may be implemented in different ways.
The capacitance C1 in the smoothing unit 41 also has the function of keeping a voltage level corresponding to the compensating signal D during the estimation of the DC component A when the first switch S1 is open and the capacitance Ct in the estimating unit 2 also has the function of keeping a voltage level corresponding to the estimate C during the updating of the compensating signal D when the second switch S2 is open.
This means that in a first state of the arrangement, when the first switch S1 is open and the second switch S2 is closed, which is as long as difference between the estimate C and the compensating signal D is within the set predefined interval E, then is the present compensating signal D represented by the voltage that is upheld by the capacitance C1 belonging to the smoothing unit 41 in the adding unit 4. If the DC component A varies enough to cause the difference between the estimate C and the compensating signal D to end up outside of the predefined interval E, then the arrangement 1 will go from its first state into a second state.
In this second state of the arrangement, the first switch S1 is closed and the second switch S2 is open, which is as long as difference between the estimate C and the compensating signal D is outside of the predefined interval E, then the present compensating signal D is replaced with an updated compensating signal D′, meaning that the voltage upheld by the capacitance C1, belonging to the estimating unit, which voltage represents the current estimate, is propagated to the capacitance C1, belonging to the smoothing unit 41 in the adding unit 4, thus representing the updated compensating signal D′. The difference between the estimate C and the compensating signal D′ will diminish as the capacitor C1 is charged to represent the updated compensating value D′ and the arrangement will go from its second state into its first state.
It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodiment thereof and that modifications can be made within the scope of the inventive concept as illustrated in the accompanying claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US5030850 *||Feb 26, 1990||Jul 9, 1991||The United States Of America As Represented By The Department Of Energy||Off-set stabilizer for comparator output|
|US5274273 *||Jan 31, 1992||Dec 28, 1993||Sperry Marine Inc.||Method and apparatus for establishing a threshold with the use of a delay line|
|US5563587 *||Mar 21, 1994||Oct 8, 1996||Rosemount Inc.||Current cancellation circuit|
|US5699256 *||Jun 1, 1995||Dec 16, 1997||Matsushita Electric Industrial Co., Ltd.||Offset-drift correcting device for gyro-sensor|
|US5760629 *||Jul 18, 1996||Jun 2, 1998||Matsushita Electric Industrial Co., Ltd.||DC offset compensation device|
|US5945864 *||Jul 14, 1997||Aug 31, 1999||Siemens Aktiengesellschaft||Circuit configuration for offset compensation|
|US5978422 *||Sep 2, 1997||Nov 2, 1999||Siemens Aktiengesellschaft||Circuit for determining and evaluating a data signal on which a direct voltage portion is superposed|
|US6417707 *||Jul 6, 1998||Jul 9, 2002||Toric Limited||Noise reduction circuits|
|US6498929||Jun 23, 1997||Dec 24, 2002||Kabushiki Kaisha Toshiba||Receiver having DC offset decreasing function and communication system using the same|
|US6535560||Jun 3, 1999||Mar 18, 2003||Ditrans Corporation||Coherent adaptive calibration system and method|
|US7095997 *||Oct 25, 2002||Aug 22, 2006||Stmicroelectronics N.V.||Direct-conversion receiver for a communication system using a modulation with non-constant envelope|
|US7155185 *||Jun 9, 2004||Dec 26, 2006||Theta Microelectronics, Inc.||Apparatus and methods for eliminating DC offset in a wireless communication device|
|US20020160738||Mar 20, 2001||Oct 31, 2002||Stephen Allott||DC offset correction for use in a direct-conversion radio architecture|
|US20030148750||Feb 7, 2002||Aug 7, 2003||Yan Kelvin Kai Tuan||DC offset correction using dummy amplifier|
|EP0863606A1||Mar 3, 1998||Sep 9, 1998||Nec Corporation||Direct conversion receiver capable of cancelling DC offset voltages|
|EP0964557A1||May 26, 1999||Dec 15, 1999||Lucent Technologies Inc.||Receiver DC offset compensation|
|WO1998038799A1||Feb 24, 1998||Sep 3, 1998||Maxim Integrated Products, Inc.||Direct-conversion tuner integrated circuit for direct broadcast satellite television|
|WO1999046852A1||Feb 22, 1999||Sep 16, 1999||Maxim Integrated Products, Inc.||Dc offset correction for direct conversion tuner ic|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8773190 *||Mar 8, 2013||Jul 8, 2014||Intel Mobile Communications GmbH||Fine RF transceiver DC offset calibration|
|US20130234773 *||Mar 8, 2013||Sep 12, 2013||Peter Mueller||Fine rf transceiver dc offset calibration|
|U.S. Classification||327/307, 327/551|
|International Classification||H03L5/00, H03D3/00|
|Jul 14, 2005||AS||Assignment|
Owner name: INFINEON TECHNOLOGIES AG, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HJELM, MIKAEL;REEL/FRAME:016531/0484
Effective date: 20050627
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